![Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59399.jpg&w=3840&q=50)
単核Fe (II) 複合体における緩慢な磁気放緩のための状態外のスピン軌道結合の重要性
Po-Heng Lin1, Nathan C Smythe, Serge I Gorelsky
1Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.
Journal of the American Chemical Society
|September 8, 2011
まとめ
2つの鉄 (II) 複合体を磁気性のために研究した. 複合体1は,スピン・軌道結合により単一分子磁石として作用し,複合体2は緩やかな磁気緩和を示さない.
科学分野:
- 無機化学 無機化学とは
- マグネト化学 マグネト化学
- マテリアルサイエンス 材料科学
背景:
- 高スピン鉄 (High-spin iron) 複合体は,磁気特性により興味を惹かれる.
- スピン・オービト・カップリング (SOC) は,磁気リラックスダイナミクスに大きな影響を与える.
- ゆっくりとした磁気放緩に影響を与える要因を理解することは,分子磁気材料の開発に不可欠です.
研究 の 目的:
- 異なる幾何学を持つ2つの単核高回転Fe (((II)) 複合体を合成し,特徴づけること.
- リガンドフィールドの幾何学が磁気特性と緩やかな磁気放松に与える影響を調査する.
- これらのFe (II) 複合体の磁気行動におけるスピン軌道結合の役割を明らかにする.
主な方法:
- 2つの単核高スピンFe(II) 複合体の合成: [Fe(II) (((N(TMS) (((2)) (((2) (((PCy ((3)))) (1) と [Fe(II) (((N(TMS) (((2)) (((2)) 深い) ] (2).
- 温度に依存する磁気感受性を含む磁気特性測定.
- 電子構造とスピン・軌道結合効果の分析.
主要な成果:
- 三角平面幾何学を持つ複合体1は,磁気化の緩やかな緩解を600 Oeで示し,フィールド誘発単分子磁石として振る舞います.
- 歪んだ四面体幾何学を持つ複合体2は,緩やかな磁気放松を示さない.
- 複合体1の低い電子興奮状態は,SOC誘発混合を促進し,軌道角運動量を基底状態に再導入します.
結論:
- リガンドフィールドの幾何学は,興奮状態へのエネルギーギャップと,SOC混合の範囲を深く影響する.
- コンプレックス1は,電子構造とSOCの制御を通じて単分子磁石の設計原理を実証しています.
- 複合体2は,より大きなエネルギーギャップがSOC効果を抑制し,ゆっくりとした磁気放松を防ぐことを強調しています.
関連する概念動画
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
01:28Atomic Nuclei: Types of Nuclear Relaxation
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers energy to a nearby...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
01:03Atomic Nuclei: Nuclear Spin State Overview
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:08NMR Spectroscopy: Spin–Spin Coupling
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...